I searched the forum for an answer to this, but couldn't find one.

I'm running:
Sibelius 7.1.3
VDL 2.5
OS Mavericks

For a couple of years, I've used this configuration with no problems.  When I upgraded to Mavericks a couple of months ago, there were no problems.  Just recently, I started getting an error message that Kontakt was running out of memory and as a result I started losing sounds.  I figured that I needed to add another instance of Kontakt to the playback settings, but since I was still using Kontakt Player 2 and I had heard that Kontakt Player 5 was now compatible, I downloaded Kontakt 5.  After setting up the typical playback settings, and a little bit of frustration getting that to work (its been a long time since I first set up VDL on this machine), the sounds all play back just fine.  The problem is, about 20 minutes into working in a file all VDL sounds stop playing back entirely.  Highlighting notes plays no sound, nor does using the playback feature.  I go to playback settings, and nothing has changed.  If I quit Sibelius and start back up, everything works just fine.  20 minutes later, the sounds stop playing back again.

Anyone have any potential fixes?  Do I need to go back to Kontakt 2?

Unfortunately there have been a number of reports of issues between Kontakt 5 and Mavericks. Have you been in touch with Native Instruments support regarding this?

Ok.  For now I'm going back to Kontakt 2.  Any insight on how to stop getting the error message ";memory is getting low";?  I've added more instances of Kontakt, I've purged and reloaded samples, I've adjusted my DFD settings.  Its pretty frustrating since everything was working fine just a week ago, and I have indoor writing to wrap up and fall writing to start.

How many instruments do you have loaded into each instance of K2? Also, in Kontakt 2, if you go to Options > DFD, what is the slider set to?

I currently have 3 instances of Kontakt open, with 16 in each of the first two, and a few overflow instruments into the 3rd.  I was running with two instances of Kontakt as was recommended when I first set up VDL with Sibelius a couple of years ago.

I've tried the DFD settings at both ends with no change in results.  Kontakt's website doesn't explain very well what the difference is.  I have 16 gigs of ram, so that part shouldn't be a problem.  I would assume that Mavericks runs in 64 bit, but if I remember correctly Kontakt 2 is 32 bit only.